1. The DX-2V in the Emtron Product Line — 6-Metre QRO Debut at Dayton 2010

The Emtron DX-2V was publicly introduced at the Dayton Hamvention, Ohio, USA, May 2010, alongside the DX-3SP. The only known contemporary documentation of the DX-2V at its introduction is the Dayton 2010 photo coverage published at cqdx.ru (attributed to photographer N8OIF), which identifies the amplifier as: “EMTRON DX-2v 6m QRO 2 KWT Linear Amplifier.” ¹ The DX-2V is also confirmed as a production model by its appearance in Dan’s complete Emtron model inventory at emtrondv.com, which lists it alongside DX-1, DX-1a, DX-1d, DX-1SP, DX-1V, DX-2, DX-2a, DX-2SP, DX-2V, DX-3, DX-3SP, and DX-4.²

The DX-2V parallels the DX-1V in the same way the DX-2 parallels the DX-1D: the V suffix denotes the six-metre (50 MHz) specialist configuration. The DX-1V is a GU74B-based 750 W 6-metre amplifier; the DX-2V is the GU84B-based 2,000 W 6-metre amplifier. In both models, the V-suffix designation indicates that the full 9-band HF tank circuit is removed and replaced with a single-band 50 MHz pi-network, the plate choke is specifically wound for 50 MHz, and QSK is factory-installed standard equipment. All other internal modules are shared with the equivalent HF model.

2. DX-2V vs DX-2 / DX-1V — Defining Differences

3. DX-2V Technical Specifications

4. The 50 MHz RF Deck — The DX-2V’s Defining Feature

The DX-2V RF deck is the entire engineering and service distinction between this amplifier and the DX-2 / DX-2A. The nine-position multiband tank assembly of the DX-2 is replaced by a single-band 50 MHz pi-network. Everything else — the GU84B tube in its RF sub-chassis, the 9-way connector, the plate bypass capacitors, the A106 protection diodes, and the AMPC board — is unchanged. The service challenges unique to the DX-2V are entirely within the 50 MHz RF deck.

4.1 Single-Band 50 MHz Pi-Network — Service Notes

5. 50 MHz Tune-Up Procedure

The DX-2V tune-up procedure differs from the multiband DX-2 in that there is no band switch to select and no coil-switching mechanical operation. The Plate and Load capacitors are the only controls. The following procedure assumes a 50 Ω non-reactive dummy load rated for 2,000 W and a 50 MHz RF source (transceiver or signal generator) capable of 30–60 W output.

  INITIAL SETUP (cold start, after servicing or tube replacement):
  ─────────────────────────────────────────────────────────────────
  1. Connect 50Ω dummy load rated ≥2,000W to RF OUTPUT.
  2. Connect 50MHz transceiver to RF INPUT.
  3. Verify earth strap connected to rear-panel wing-nut.
  4. Power ON; wait for READY LED.
  5. Switch to OPR; key transceiver at 2–3W carrier (RTTY or CW).

  INITIAL PLATE CAPACITOR POSITION:
  ─────────────────────────────────────────────────────────────────
  6. Set Plate capacitor to approximately 40% meshed (from minimum).
     This is the approximate 50MHz starting point.
  7. Set Load capacitor to approximately 30% meshed (light loading
     for initial tuning pass).

  DIP AND LOAD:
  ─────────────────────────────────────────────────────────────────
  8. Increase drive to 10W. Rotate Plate slowly until plate current
     (Ip bargraph) shows a DIP (minimum current = resonance).
     Do NOT adjust at full power during initial setup.

  9. Increase Load slightly (more meshed) to increase forward power
     reading. Re-dip Plate for minimum Ip.

  10. Repeat dip/load steps incrementally, increasing drive power in
      stages (10W → 25W → 50W → full power).
      At each step: dip Plate, increase Load, confirm Ip
      dips rather than rises with Plate adjustment.

  FINAL SETTING:
  ─────────────────────────────────────────────────────────────────
  11. At full drive (30–60W), verify forward power approaches 2,000W
      on bargraph (calibrate per VR1/RF F if required) with Ip at
      or below 0.85A.
  12. If Ip exceeds 1.0A at full drive, reduce Load (unmesh) slightly
      and re-dip Plate. A 50MHz pi-network has higher Q than an HF
      network; each adjustment step has more effect than on HF bands.
  13. Record final Plate and Load settings in the manual title page
      for future reference. The 50MHz pi-network settings are fixed
      (no band switching); these values do not change.

  SIGNS OF PROBLEM:
  ─────────────────────────────────────────────────────────────────
  ○ No Ip dip across full Plate range → plate choke issue or
    bypass capacitor failure at 50MHz.
  ○ Ip rises sharply with any Plate adjustment → parasitic
    oscillation or mistuned input network.
  ○ Drive required exceeds 80W for full output → input matching
    network detuned or failed; input SWR elevated at 50MHz.

Figure 1. DX-2V 50 MHz tune-up procedure — single-band; no band switch; higher-Q pi-network than multiband HF amplifiers.

6. GU84B Tetrode — 50 MHz Operation & Service

The GU84B in the DX-2V operates at 50 MHz, which is only 20% of its rated 250 MHz maximum frequency. The tube itself is well within its design envelope at 6 metres; there are no tube-specific limitations for 50 MHz operation. All standard GU84B service procedures from the DX-2 guide apply: 27 V / 3.7 A heater, 3-minute warm-up, NOS gettering procedure (12–16 hours heater-only for NOS tubes), bias target 370–380 mA, temperature sensor position.

At 50 MHz and 2,000 W output, the GU84B’s inter-electrode capacitances are more significant than at HF. The G1 input capacitance (~100 pF) loads the input matching circuit; the plate-to-grid feedback capacitance (Cpg ~8 pF) can cause instability if the plate and grid circuits are not properly shielded and decoupled at 50 MHz. Emtron’s design addresses this with the anode parasitic suppressor; never operate the DX-2V without this suppressor in place.

7. Shared Modules — Identical to DX-2; Cross-Reference to DX-2 Guide

All modules outside the 50 MHz RF deck are identical to the DX-2 and are fully documented in the DX-2 guide. The service notes below are brief summaries with cross-references:

8. Safety Systems — Interlocks, Discharge & RF Hazards at 50 MHz

8.1 Cover Safety Microswitch

The DX-2V cover safety microswitch is identical to the DX-2. At 50 MHz and 2,000 W, the RF field inside the cabinet when transmitting is significantly more hazardous than at lower HF frequencies; the RF power density at 50 MHz from a 2,000 W source is such that even brief exposure to open RF structures inside the cabinet can cause RF burns. Never operate the DX-2V with the cover removed except under the controlled conditions of safety microswitch defeat required for specific adjustment procedures, and never key the transmitter at power during internal inspection.

8.2 Safe Discharge Procedure

  STEP 1 ── OPR → STBY; POWER → OFF.
               │
  STEP 2 ── DISCONNECT ALL REAR PANEL LEADS immediately:
            Mains cord, RF INPUT, RF OUTPUT, PTT/Key,
            ALC cable, control cables.
               │
  STEP 3 ── Wait MINIMUM 5 MINUTES.
            DX-2V HV filter bank at 2,500V DC; same
            discharge time requirement as DX-2.
               │
  STEP 4 ── ANODE DISCHARGE:
            10kΩ/25W resistor with insulated clip leads.
            Clip one end to chassis; firmly contact other
            end to GU84B anode cap. Hold 15 seconds.
            Do NOT contact any 50MHz tank components
            during discharge (high RF impedance nodes).
               │
  STEP 5 ── HV MEASUREMENT:
            4,000V-rated DMM.
            Confirm HV filter cap positive to chassis < 50V DC.
               │
  STEP 6 ── SCREEN SUPPLY:
            Measure EG2 (blue wire) to chassis → < 50V.
               │
  STEP 7 ── BIAS SUPPLY:
            Measure –Eg1 to chassis → within −10V.
               │
  STEP 8 ── RE-VERIFY HV: < 10V DC.
               │
  STEP 9 ── TEMPERATURE SENSOR POSITION:
            Verify both sensors above GU84B near-horizontal.
            High voltage between sensors and tube anode.
               │
  STEP 10 ── SAFE: all rails < 10V. Work may begin.
             Keep one hand behind back while probing.

Figure 2. DX-2V safe discharge procedure — same voltage hazard as DX-2; includes reminder not to contact 50 MHz tank components before discharge is confirmed.

9. Safety Capacitors — X2 and Y2 Requirements

The DX-2V soft-start module safety capacitors are identical to the DX-2 and are documented in the FCC filing for the DX-1B (document Q8VDX1B, soft-start schematic 15.6), which applies across the DX series. Replacement with non-certified types is prohibited.

10. RF Sensor — Forward Power Calibration at 2,000 W / 50 MHz

The DX-2V RF sensor must be calibrated at 2,000 W on 50 MHz. The directional coupler in the RF sensor has frequency-dependent coupling characteristics; the coupling factor at 50 MHz may differ from the HF calibration point. Calibrate with a Bird 43 fitted with a 50 MHz element (2500H, 2500W, or equivalent 2,500 W element) or equivalent calibrated wattmeter at 50 MHz. Adjust VR1 (RF F) for correct display indication at 2,000 W forward power on 50 MHz. If no 50 MHz calibrated wattmeter is available, a minimum power calibration can be performed at lower power and linearly extrapolated, but this is less accurate. Always verify SWR protection trips correctly at the correct SWR threshold on 50 MHz after any sensor calibration change.

11. Cabinet, Front Panel & Assembly Hardware

The DX-2V cabinet is built to the same standard as the DX-2: 2 mm steel chassis with dark yellow chromate coating, 3 mm anodised aluminium front panel, and baked enamel texture finish. The front panel of the DX-2V is the most visually distinctive difference from the DX-2 — there is no band switch knob, and the panel silk-screen identifies the amplifier as a 6-metre / 50 MHz unit. The Tune and Load controls are present as on all DX models, plus the standard front-panel LED indicators and the power/STBY-OPR switches.

12. Parts Sources & Reference Documents

• emtrondv.com — Dan — emtrondv.com — Version 7 AMPC control board (DX-2V compatible); plate choke (stocked — specify DX-2V 50 MHz application); limited module stock; free technical advice; refurbished Emtron amplifiers (Sydney pickup). Dan is the only known source for original DX-2V RF deck specifications including the 50 MHz plate choke, pi-coil inductance, and input matching network details.
• Dayton 2010 DX-2V Primary Source — cqdx.ru — Photo report from N8OIF at Dayton Hamvention 2010; first published documentation of the DX-2V as a production Emtron amplifier rated 2,000 W on 6 metres.
• Emtron DX-2 Operating Manual — manualslib.com — Service procedures for all modules shared with DX-2V: AMPC board, soft-start, HV supply, display board, RF sensor. RF sub-chassis schematic (Section 16.6) applies to DX-2V tube circuit (plate bypass, A106 protection diodes, etc.).
• Emtron DX-1B FCC Filing (Schematic Set) — fccid.io/Q8VDX1B — Complete soft-start, QSK, and control board schematics applicable to the DX-2V. The soft-start safety capacitor types (Y2: 4.7 nF; X2: 470 nF and 220 nF) are documented here.
• GU84B Datasheet — ok1rr.com — Input capacitance, transconductance, and maximum frequency data essential for understanding the DX-2V’s 50 MHz design constraints.
• GU84B Tube Sources (NOS) — DL3JJ / QRO-Shop (qro-shop.com); RF Parts Co. (rfparts.com); Soviet-Tubes.com. NOS tubes require 12–16 hours heater-only gettering; verify 27 V heater at tube socket before installation.
• W8JI VHF Stability Reference — w8ji.com/vhf_stability.htm — Tom Rauch W8JI’s comprehensive reference on parasitic oscillation and suppression in HF/VHF amplifiers. Essential background reading for servicing the DX-2V parasitic suppressor network.
• W8JI Plate Choke Design Reference — w8ji.com/rf_plate_choke.htm — Tom Rauch W8JI’s reference on RF plate choke design and self-resonance testing. Essential for verifying or replacing the DX-2V’s 50 MHz plate choke.
• Bird Model 43 50 MHz Elements — RF Parts Co. (rfparts.com); Telewave. Bird 2500H (25–60 MHz / 2,500 W) or 2500W element for full-power DX-2V RF sensor calibration at 50 MHz.